When a trailer is being towed by an automobile, there is often a tendency for the trailer to move about the yaw axis relative to the towing vehicle, thereby inposing substantial lateral forces upon the rear end of the vehicle. In severe cases, such as under strong wind conditions, the yaw effects may be considerable and may render the towing vehicle uncontrollable. It is also desirable to permit relative movement between the towing vehicle and the trailer and to cushion and damper vertically directed shock forces.